Analyzing the mechanism of reducing B content on the coercivity of sintered (Nd, Ce)-Fe-B magnets

Abstract

In recent years, the research focus has shifted towards the preparation of non-heavy rare earth (RE)-Fe-B magnets with high coercivity (Hcj) by reducing the content of B element. In this work, we achieved resource-saving sintered (Nd, Ce)-Fe-B magnets by adjusting the B element content, optimizing microstructure, and enhancement of Nd/Ce element distribution. We conducted an analysis on the magnetic characteristics, phase composition, microstructure, magnetization reversal mechanism, and economic viability of these sintered magnets. With a decrease in the B element content from 0.96 wt% to 0.90 wt%, there is a increase of approximately 1 kOe in Hcj.At the same time, the temperature coefficient of Hcj has been improved, resulting in a absolute value decrease from 0.67%/°C to 0.63%/°C. The findings suggested that reducing the mass fraction of B element could facilitate the formation of a thicker grain boundary phase between the grains. It could significantly weaken the ferromagnetic coupling effect, and enhance the magnetic isolation effect between grains, resulting in a higher Hcj. From an economic perspective, compared to the cost of magnet with similar coercivity prepared by increasing the RE content, the cost of magnet with low B element content was reduced by 554.4 US$/t, approximately saving 3.08%. This study provides a new theoretical foundation and experimental basis for resource-saving sintered (Nd,Ce)-Fe-B magnet preparation.